1. Field of the Invention
The present invention relates to a hologram recording medium on which data is recorded in the form of a hologram, an apparatus for reproducing data from a hologram recording medium, and a method of reproducing data from a hologram recording medium.
2. Description of the Related Art
It is known to record information on a sheet-shaped recording medium such that the information is recorded in the form of a one-dimensional code or a two-dimensional code such as a bar code, a QR code, or a dot code (see, for example, Japanese Unexamined Patent Application Publication No. 2005-173646). However, this type of information recording medium is very low in storage capacity per unit area. For example, the typical storage capacity is in the range from several ten bytes to several kilo bytes. This very low storage capacity is simply because of its physical limitation on the resolution of printing a black-and-white pattern.
It is also known to use a hologram recording medium as a sheet-shaped recording medium that allows various kinds of data to be recorded in the form of an interference fringe produced as a result of interference between object light and reference light. It is known that the hologram recording medium has a very large storage density and thus the hologram recording medium is very large in storage capacity. For example, the hologram recording medium is expected to be very advantageously usable as a high-capacity storage medium for storing computer data or content data such as audio data or video data.
In the hologram recording medium, data is recorded in the form of an image of two-dimensional page data. When the image of the data is displayed on a liquid crystal display panel or the like, if light is passed through this liquid crystal display panel, object light of the image is obtained. The resultant object light of the image of the two-dimensional page data is focused on the hologram recording medium. In this state, the hologram recording medium is illuminated with a reference light such that the reference light falls on the hologram recording medium at a predetermined angle. As a result, interference occurs between the object light and the reference light, and an interference fringe is produced. The resultant interference fringe pattern is recorded as one element hologram in the form of a dot or a strip. That is, one page of two-dimensional page data is recorded as one element hologram.